Conventionally, a plug door device to be installed at an entrance of a vehicle for performing an operation of opening and closing a door and a plugging operation of moving a door in a vehicle width direction is known (e.g., see Patent Literature 1). The plug door device disclosed in Patent Literature 1 is configured as a plug door device for opening/closing a pair of doors, which are two-panel sliding doors, installed at an entrance. This plug door device includes a fixed base fixed to the vehicle body, a slide base provided on the fixed base movably in a vehicle width direction, and a door drive mechanism provided as a door driver that is installed on the slide base and moves the doors in front and rear directions of the vehicle via a connecting portion.
Also, the plug door device of Patent Literature 1 is further provided with a shaft portion provided in the connecting portion, and a guide portion that is rotatably provided on the fixed base, pivots while coming into contact with the shaft portion and guides the shaft portion such that the shaft portion moves toward one side in the vehicle width direction when the doors open, and pivots while coming into contact with the shaft portion and guides the shaft portion such that the shaft portion moves toward the other side in the vehicle width direction when the doors are closed. This plug door device is thereby configured as a small plug door device capable of performing the opening/closing operation and the plugging operation using the door drive mechanism for causing a force in the front-rear direction of the vehicle to act on the doors.
Also, the plug door device of Patent Literature 1 is configured such that the door drive mechanism for moving the doors in the vehicle front-rear direction via the connecting portion includes a rack-and-pinion mechanism for moving the connecting portion. This rack-and-pinion mechanism is configured such that a driving force of an electric motor is input to a pinion via a planet gear mechanism, and a pair of racks that mesh with the pinion move in opposite directions.
Also, the plug door device of Patent Literature 1 includes a locking mechanism capable of locking the doors so as to restrict the movement of the doors at a door closed position. Further, Patent Literature 1 recites that a locking mechanism disclosed in Patent Literature 2 can be used as the aforementioned locking mechanism.
Meanwhile, the locking mechanism disclosed in Patent Literature 2 is configured to be able to lock the movement of doors as a result of being engaged with a locking pin provided on the door side when the doors are at the closed position. This locking mechanism is configured to include a link mechanism that can be deformed into a linear state and into a bent state, and a link retaining mechanism that is pivotably installed in the vicinity of both ends of the link mechanism and retains the link mechanism in a bent state when the doors are at a position other than the closed position. The link retaining mechanism is configured as a pair of engaging members including a first engaging portion that is engaged with the locking pin at the closed position and a second engaging portion that is engaged with an end of the link mechanism in a linear state at the same closed position. The locking mechanism is thereby configured to be able to lock the door movement.
Also, the plug door device of Patent Literature 1 is provided with an upper pivoting arm and a lower pivoting arm that pivot respectively on the upper side and the lower side of the entrance and thereby guide the doors in the vehicle width direction so as to assist the plugging operation of the doors. A roller is provided at the tip of each of the upper pivoting arm and the lower pivoting arm, and each roller is disposed movably along a groove of a rail provided on the doors. Also, a connecting rod is provided between the upper pivoting arm and the slide base, one end of the connecting rod is provided pivotably relative to the upper pivoting arm side, and the other side thereof is provided pivotably relative to the slide base.
Furthermore, the plug door device of Patent literature 1 is provided with a connecting shaft that extends in up-down direction and is supported pivotably relative to a bracket provided at the entrance. This connecting shaft is configured to connect the upper pivoting arm and the lower pivoting arm, the upper pivoting arm is fixed on the upper end side of the connecting shaft, and the lower pivoting arm is fixed on the lower end side of the connecting shaft. With the above configuration, in the plug door device of Patent Literature 1, the upper pivoting arm pivots via the connecting rod with the movement of the slide base, and further, the lower pivoting arm also pivots via the connecting shaft with the pivoting of the upper pivoting arm. Thus, the plug door device of Patent Literature 1 is configured to prevent occurrence of a state where the movement of the door at its lower side does not sufficiently follow the movement of the door at its upper side where the shaft portion, the guide portion, and the slide base are disposed during the plugging operation, even if the rigidity of the doors is small.